Apparatus for producing phosphorus



y 7, 1938, H. A. cuRT xs ET AL 2,117 301 APPARATUS FOR PRODUCING P HOSPHORUS Filed Dec. 7, 1955 2 Sheets-Sheet l ROTARY ELECTRIC C NDENSERS BLOWER KILN FURNACE HOSPHATE COKE ROCK I I7 ILICA m 1 k LAG FERROPHOSPHORUS FIG. I

ROTARY ELECTRIC CONDENSERS BLCWER KILN FURNACE PHOSPHATE ROCK , LAG PHosPHoRus FERROPHOSPHORUS Ha fry A. Cu n is Ecz mond L- Co oson INVENTORS BY WKLDW ATTORNEY May 17, 1938. H, A. CURTIS ET AL 2,117,301.

APPARATUS FOR PRODUCING PHOSPHORUS Filed D80 '7, 1935 2 Sheets-Sheet 2 COKE FERROPHOSPHORUS AG FiJsan PHosPHAfi j ROCK a SILICA 7 a v. J

SLAG

FERROPH SPHORUS LAG FERROPHOSPHORUS FIG.4

hbrryA. Curr/s Raymond L- Copson INVENTORS Y QMIM ATTORNEY Patented May 17, 1938 APPARATUS FOR PRODUCING PHO SPHORUS Harry A. Curtis, Knoxville, Tenn, and Raymond L. Copson, near Sheffield, Ala.

Application December 7, 1935, Serial No. 53,325

4 Claims.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended Apri 30, 1928, and the invention herein described, if patented, may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates 'to an apparatus for producing elemental phosphorus by the electric furnace method, particularly by the use of a resistance type electric furnace.

One of the objects of this invention is to provide a means for the production of elemental phosphorus which eliminates the difliculty of disposing of the residual carbon monoxide, containing very small proportions of phosphorus which can only be removed with considerable difficulty. Another object of this invention is to-utilize the calorific value of the carbon monoxide in the gaseous reduction products. Still another object of this invention is to utilize more effectively the electric power required in an electric phosphate reduction furnace. Other objects of this invention include the provision for more favorable conditions for reaction between the constituents of a phosphate reduction furnace charging stock.

We have discovered a novel combination of apparatus for the more economical production of elemental phosphorus which comprises a furnace for melting the phosphate rock and silica portions of the phosphate furnace charging stock, an enclosed resistance type electric furnace with a hearth below the electrodes on which a molten mixture of the phosphate rock and silica portion of the charge is reduced by carbon heated to incandescence during its passage between the electrodes, and an indirectly cooled condenser for condensing and separating the major portion of the elemental phosphorus from the phosphate reduction furnace gas produced in the electric furnace.

In the accompanying drawings, which form a part of the specification, and wherein reference symbols refer to like parts whenever they occur,

Fig. 1 is a diagrammatic, plan view of one form of apparatus for the embodiment of our invention,

Fig. 2 is a diagrammatic, vertical, sectional view 7 of the form of apparatus shown in Fig. 1,

Fig. 3 is a diagrammatic, plan view of one form of an enclosed resistance type electric furnace for reduction furnace charging stock are fed to a rotary kiln I, which is fired with a phosphate reduction furnace gas, from which the major portion of the elemental phosphorus has been removed, admitted to the burner through line 3. The mixture of the phosphate rock and the silica is fused in the rotary kiln I, withdrawn through line 5, and delivered to the electric furnace I, below the electrodes 9, and adjacent to the level of zone of maximum temperature in the furnace between the electrodes 9. Coke is fed to the zone above the top of the electrodes 9, through a plurality of inlets located in the top of electric furnace I, to a predetermined height, which is sufficient to submerge the coke, heated to incandescence between the electrodes 9, to substantially the entire .depth of the molten mixture of phosphate rock and silica in the bottom of the furnace. The calcium silicate slag and the ferrophosphorus formed are withdrawn from the furnace hearth at points substantially opposite the point of admission of the molten mixture of phosphate rock and silica. The gas produced by the reduction of the molten mixture of phosphate rock and silica by the coke, consisting of carbon monoxide and elemental phosphorus, rises through the coke portion of the charge and is withdrawn from the top or near the top of the furnace I, through line I i The phosphate reduction furnace gas passes from line H to condenser l3, where the gas is cooled indirectly by the use of water to a temperature not lower than the melting point of elemental phosphorus, The major portion of the elemental phosphorus is condensed to a liquid and is withdrawn from the bottom of condenser 13. The cooled gas, from which a substantial portion of the phosphorus has been removed, still contains some liquid phosphorus in suspension as well as some uncondensed phosphorus. This gas passes from condenser 13, through line l5, to condenser-separator H, which is also cooled indirectly by water to a temperature not below the melting point of phosphorus. Some further condensation of elemental phosphorus is thereby effected together with the separation of the elemental phosphorus which was condensed in condenser i3, but which had not separated by the time the gas left that condenser. The gas leaving condenser-separator I'I, still contains a very small portion of elemental phosphorus which is not condensable at the temperature of the melting point of phosphorus. This gas is withdrawn through line I9 through the inlet of blower 2i, which serves to maintain a substantially atmospheric pressure in electric furnace l, and is discharged into line 3, as the fuel for fusing the mixture of the phosphate rock and silica in the rotary kiln i.

It is evident that there are numerous factors which will influence conditions for the most satisfactory operation of our invention, the actual limits of which cannot be established except by a detailed study of each set of raw materials and the intermediate and finished products involved.

The phosphate rock and the silica are used in the proper stoichiometrical proportion for reduction with incandescent carbon to form elemental prosphorus and a calcium silicate slag of the dsired melting point.

The mixture of the phosphate rock and silica may be fused in any suitable type furnace, such as a shaft furnace or a rotary kiln. The mixture of the phosphate rock and silica may be fused by the use of any suitable fuel but we have found it most economical and most advantageous, from the standpoint of the disposal of the traces of phosphorus remaining in phosphate reduction furnace gas after the removal of the major portion of the elemental phosphorus by conventional condensing means, to use this phosphate reduction furnace gas containing only traces of elemental phosphorus as a source of the fuel. This trace of elemental phosphorus is converted to rests on the hearth of the furnace.

phosphorus pentoxide during the combustion of the gas with the required amount of air and the phosphorus pentoxide so formed reacts with the phosphate rock and thereby eliminates a hazard and a nuisance.

The enclosed electric furnace used has a steel shell and a refractory lining. It is preferably a three phase alternating current resistor furnace,

phosphate rock and silica on one side and outlets for the calcium silicate slag and the ferro phosphorus formed substantially opposite the inlet.

A solid carbonaceous material, preferably coke, charged into the furnace above the elevation of the electrodes either through one or a plurality of inlets is heated to incandescence as it serves as an electrical resistor during its passage between the electrodes. The column of coke above the elevation in the top of the molten liquid on the hearth is maintained at a sufllcient height to submerge the incandescent carbon passing from the zone between the electrodes into the molten liquid on the hearth so that the column of coke actually By this means it is possible to maintain an intimate contact between the reactants, with incandescent coke being supplied for the reaction automatically as the carbon in the coke in contact with the molten portion of the charge reacts to form carbon monoxide.

Although it is ordinarily preferable to use a solid carbonized material, such as coke, for accomplishing the reduction in this process, under certain circumstances solid uncarbonized materials may be charged in place of the solid can may be used as a source of the carbon required for the reaction.

The major portion of the elemental phosphorus contained in the phosphate reduction furnace gas produced by our process may be separated from the uncondensed constituents of the mixture by direct or indirect cooling with water, with the indirect cooling being preferable. One or a plurality of condensers may be used with one or more oi? the condensers serving as separators for the removal of the major portion of the phosphorus mist from the gas after the elemental phosphorus has been condensed to a liquid state. The temperatures to which the gas may be cooled during condensing will vary depending upon the design and number of condensers or condenser-separators used. In any event the temperature in the gas will not ordinarily be reduced to below the melting point of phosphorus in order that the liquid phosphorus separated. may be readily withdrawn.

It will be seen, therefore, that this invention actually may be carried out by the modification or certain details without departing from its spirit or scope.

We claim:

1. An enclosed resistance type electric furnace for the reduction of a phosphate furnace charging stock to produce elemental phosphorus, which comprises, in combination with the furnace shell and hearth, an inlet on one side of the hearth for the admission of the molten phosphate rock and silica to the furnace at an elevation below its electrodes, an outlet to the hearth substantially opposite the above inlet for the withdrawal of calcium silicate slag, an outlet below and adjacent to the above outlet for the withdrawal of ferrophosphorus, a plurality of electrodes located in the wall of the furnace above and adjacent to the level of the molten liquid in the hearth, an inlet in the top of the furnace shell for admission of the carbonaceous material used for the reduction of the phosphate rock and silica portion of the charge, a furnace wall of such a height that ratio of the maximum depth to which the melt on the hearth is to be maintained to the distance from the top of the melt so maintained to the top of the furnace is inversely proportional to the ratio of the density of the melt to the density of the solid carbonaceous material charged, and an outlet for the phosphate reduction furnace gas in the top of the furnace shell.

2. An enclosed electric furnace for the reduction of an ore with a solid carbonaceous reducing agent in the presence of a flux, which comprises in combination with the furnace shell and hearth, an inlet in the top of the furnace shell for the admission of the solid carbonaceous reducing agent to form a column of the same within the shell; a plurality of electrodes located in the wall of the furnace above and adjacent to the molten liquid level in the hearth and making contact with the solid carbonaceous reducing agent so that the latter, free from the ore and the flux portion of the charge, serves as an electrical resistor upon the application of an electric current to the electrodes; an inlet on one side of the hearth for the admission of the ore and the flux in'a molten condition to the furnace at an elevation below the electrodes;

an outlet to the hearth substantially opposite the above inlet for the withdrawal of slag; an

outlet below and adjacent to the last mentioned outlet for the withdrawal of the metal or metal alloy produced; a furnace wall of such a height that ratio of the maximum depth to which the melt on the hearth is to be maintained to the distance from the top of the melt so maintained to the top of the furnace is inversely proportional to the ratio of the density of the melt to the density of the solid carbonaceous, material charged; and an outlet for the reduction furnace gas through the furnace shell above the elevation of the electrodes.

3. An enclosed electric furnace for the reduction of an ore with a solid carbonaceous reducing agent in the presence of a flux, which comprises, in combination with the furnace shell and hearth, equipped with an inlet for the reducing agent and outlets, respectively, for the furnace gas, slag and metal or metal alloy produced, a furnace wall of such a height that ratio of the maximum depth to which the melt in the hearth is to be maintained to the distance from the top of the melt so maintained to the top of the furnace is inversely proportional to the ratio of the density of the melt to the density of the solid carbonaceous material charged, a plurality of electrodes above and adjacent to the molten liquid level in the hearth and making contact with the solid carbonaceous reducing agent so that the latter, out of contact with the ore and the flux portion of the charge, serves as an electrical resistor upon the application of an electric current to the electrodes; and at least one inlet to the hearth for the admission of the ore and the flux in a molten condition to the furnace at an elevation below the electrodes.

4. An enclosed electric furnace for the reduction of an ore with a solid carbonaceous reducing a ent in the presence of a flux which cornprises, in combination with the furnace shell and hearth, equipped with an inlet for the reducing agent, outlets, respectively, for the furnace gas, slag and metal or metal alloy produced, and a plurality of electrodes above and adjacent to the molten liquid level in the hearth and making contact with the solid carbonaceous reducing agent so that the latter, out of contact with the ore and the flux portion of the charge, serves as an electrical resistor upon the application of an electric current to the electrodes, a furnace wall of such a height that ratio of the maximum depth to which the melt in the hearth is to be maintained to the distance from the top of the melt so maintained to the top of the furnace is inversely proportional to the ratio of the density of the melt to the density of the solid carbonaceous material charged, at least one inlet to the hearth for the admission of the ore and the flux in a molten condition to the furnace at an elevation below the electrodes.

HARRY A. CURTIS. RAYMOND L. COPSON. 

